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There are 20 feet of blood vessels in each square inch of human skin.
Although puberty usually occurs in the early teenage years, the world's youngest parents were two Chinese children who had their first baby when they were 8 and 9 years of age.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Although not all of the following muscle groups are commonly used, intramuscular injections may be given into the abdominals, biceps, calves, deltoids, gluteals, laterals, pectorals, quadriceps, trapezoids, and triceps.
More than one-third of adult Americans are obese. Diseases that kill the largest number of people annually, such as heart disease, cancer, diabetes, stroke, and hypertension, can be attributed to diet.
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